Anti-theft cap for a screwthreaded base

ABSTRACT

An anti-theft cap for a screwthreaded base. Said cap comprises a plate provided with a tapped aperture complementary to the screwthread of the base, a body journalled on said plate and in which body a lock is mounted. Said lock comprises a catch which, for one position of the lock, is at a distance from the axis of the cap equal to that of a stop integral with said plate, and, for at least one other position of the lock, is at a different distance. Said stop is elastically movable and adapted to move under the action of the catch when the screwing torque transmitted by said catch exceeds a given value.

The present invention relates to an anti-theft cap for a screwthreadedbase, in particular for the fuel tank of a vehicle.

Such caps are known which comprise a plate having a tapped bore which iscomplementary to the screwthreaded portion of the base, a bodyjournalled on said plate, in which body a lock is mounted, said lockcarrying a catch which, for one position of the lock, is at a distancefrom the axis of the cap equal to the distance of a stop integral withsaid plate, and, for at least one other position of the lock, is at adifferent distance.

The actuation of the lock, which can only be achieved with its key,brings the catch to its second position in which, upon rotation of thebody with respect to the plate in the screwing direction, the catchencounters the stop which is in its path. Thenceforth, the body and theplate are inter-connected to rotate in the screwing direction and thecap can be screwed on the base. After this screwing, the user actuatesthe lock to bring the catch to its first position and theinterconnection between the body and the plate is eliminated so that thecap can no longer be unscrewed. For the unscrewing, the procedure is thesame, but in the unscrewing direction.

However, these known caps have the drawback that the user is liable toscrew the cap too tightly on the base, which renders the unscrewingdifficult and damages the screwthreads and/or the stops.

An object of the invention is to overcome these drawbacks of known capsby means of a tightening torque limiter.

According to the invention, there is provided a cap wherein said stop iselastically movable and arranged to move under the action of the catchwhen the screwing torque transmitted by the catch exceeds a given value.

In one embodiment of the invention, said stop is rotatable about an axisparallel to the axis of the cap and returned elastically to its stopposition, the travel of said stop being limited in one direction ofrotation by an abutment integral with said plate. This limitation of therotational travel of the stop permits preventing its rotation forunscrewing. In this case, it is advantageous to arrange that said stopis constituted by an arm of a pivoted lever whose other arm iselastically deformable.

In a modification, the stop is movable in translation substationally inthe radial direction against the action of elastic means, and has acurved profile, which cooperates with said catch so as to move the stopfor one direction of rotation of the body, and a substantially radialsecond profile.

An understanding of the invention will be had from the ensuingdescription with reference to the accompanying drawings in which:

FIG. 1 is an axial sectional view of a cap according to one embodimentof the invention;

FIG. 2 is a sectional view taken on line II--II of FIG. 1;

FIGS. 3 to 6 are views of a detail of the cap shown in FIG. 2 in respectof various positions, and

FIG. 7 is similar to FIG. 3 in respect of a modification.

With reference first to FIGS. 1 and 2, the cap, adapted to be screwedonto a screwthreaded base 1, comprises a plate 2 provided with a flange3 defining a tapped aperture 4 which is complementary to the screwthreadof the base 1. The body 5 of the cap is constituted by a cup 6 having acentre depending portion 7 which is pinned to a hub 8. The hub 8 and thedepending portion 7 extend through a centre aperture 9 of the plate 2,the hub 8 having a radial flange 10 which is rotatable on the plate 2with interposition of a ring 11. The plate 2 carries a sealing element12 cooperating with the edge of the base 1. The outer peripheral edge 13of the cap 6 overlaps the periphery of the plate 2 so that, when the capis in position on the base 1, this base is inaccessible.

A barrel-type lock 14, actuated by a key 15, is mounted in an eccentricposition in the cup 6. The barrel of the lock 14 is extended, at the endthereof opposed to the key, by a substantially semi-cylindrical catch16. A pivotable cover 17 is adapted to close the opening for the key inthe lock 14.

The plate 2 carries a pin 18 on which there is pivotably mounted acranked lever 19 retained by a washer 20. The lever 19 is of plasticsmaterial and has a substantially radial short rigid arm 21 and flexibleelongated arm 22 which is substantially perpendicular to the arm 21. Thearm 21 has a curved profile 23 adapted to cooperate with the curvedportion of the catch 16. The arm 22 is disposed in a recess 24 whichlimits the movements of the arm 22 and has an edge 25 adjacent the arm21 which acts as an abutment for the latter.

The cap operates in the following manner:

Having brought the lock to the open position by means of the key, thecatch 16 is at the same distance from the axis of the cap as the profile23 of the arm 21. Upon rotating the cup 6 in the direction of arrow V(FIG. 3), the catch 16 engages in the profile 23 and interconnects thecup 6 and the plate 2 for rotation in the screwing direction of arrow V.The cap can now be screwed onto the base 1.

As soon as the screwing is sufficient, the resistant torque resultingfrom friction between the tapped aperture 4 of the plate 2 and thescrewthreaded base 1 increases. This resistant torque is transmitted tothe arm 21 by the catch 16 and converted into a pivotal torque about thepin 18. The arm 21 starts to pivot about this pin (FIG. 3), with the arm22 bearing against the wall of the recess 24 and deforming elastically.For a value of the resisting torque which depends on the rating of theelasticity of the arm 22, the catch 16 escapes from the profile 23 ofthe arm 21 (FIG. 4). The cup 6 is released from the plate 2 and thescrewing of the plate 2 ceases. If the user, after having caused the cup6 to turn through a complete revolution, returns the catch 6 in front ofthe arm 21, the lever arm 19 having meanwhile resumed its initial shape,this arm 21 will again move away as before without producing additionalscrewing of the plate 2.

If the user turns the cup in the unscrewing direction (arrow DV, FIG. 5)the catch 16 comes in contact with the arm 21 of the lever 19, whichcannot pivot about the shaft 18, since it encounters the edge 25 of therecess 24. The plate 2 and the body 5 are therefore interconnected torotate in the direction of arrow DV and the cap is unscrewed.

When the user brings the lock to the closing position (FIG. 6) andwithdraws the key, the cap can no longer be unscrewed since the catch 16has rotated through half a revolution and no longer encounters the arm21 of the lever 19 when the body 5 is turned with respect to the plate2, so that this body 5 is freely rotatable with respect to the plate.

With reference now to the modification shown in FIG. 7, the lever 19 isreplaced by a slidable stop 26 guided in a cavity 27 and biasedoutwardly of the cavity by a coil spring 28. The stop 26 has a curvedprofile 29 cooperable with the catch 16 to produce the retraction of thestop in the screwing direction for a given resistant torque. The stop 26has a radial profile 30 which precludes any movement when the catch 16encounters it in rotating in the unscrewing direction DV.

What is claimed is:
 1. An anti-theft cap for a container having a screwthreaded opening comprising a screw threaded closure member forcooperation with said screw threaded opening, stop means on said closuremember, a cap member secured to and rotatable about said closure member,a lock fixedly connected to said cap member and including a catchelement movable, upon operation of said lock, between a first and asecond position, said catch element in said first position engaging saidstop means and in said second position being disengaged from said stopmeans, rotation of said cap member with said catch in said firstposition imparting torque to said closure member and said cap memberbeing freely rotatable on said closure member with said catch in saidsecond position, said stop means comprising a pivoted lever elasticallydeflectable out of engagement with said catch element upon theapplication of a torque greater than a predetermined limit upon rotationof said cap member in one direction and abutment means on said closuremember engaging said lever and preventing deflection of said lever uponrotation of said cap member in the opposite direction, and wherein saidlever is a bell crank lever, one limb of which is substantially rigidand engages said catch element and the other limb of which iselastically deformable.
 2. A cap as claimed in claim 1 wherein saidlever is pivoted about an axis substantially parallel to the axis ofsaid screw threaded closure member.